Method for washing coloured clothes in a domestic washing machine

ABSTRACT

A method for washing coloured clothes in a domestic washing machine comprises a preliminary phase in which water and an additive containing a colour protector compound are added to the tub, a tumbling phase in order to allow wetting of clothes and a spinning phase for removing at least a portion of water and additive from clothes before starting a washing program, the temperature of water and additive being preferably comprised between 5° C. and 30° C.

The present invention relates to a method for washing coloured clothesin a domestic washing machine comprising a washing tub.

It is well known in the art of domestic appliances that a washingprogram of a domestic washing machine comprises a first washing phase inwhich water and detergent are added to the washing tub, followed by atumbling phase in which the clothes are moved inside a drum rotating inthe tub in order to guarantee the proper interaction between detergentand clothes, a rinsing phase during which detergent is removed fromclothes and a rinsing agent or conditioner is added to clothes, and afinal spinning phase in which rinsing water is mostly removed fromclothes. Of course there can be differences in the basic washing program(for instance there can be a pre-washing phase for particularly dirtyclothes), but basically the above phases are always present in knownwashing programs.

A technical problem encountered in washing machines using traditionalwashing programs is the colour fading and the colour transfer. These aretwo well known phenomena that affect negatively the washing process ofcoloured garments.

The colour fading is the loss of colour of a coloured garment that intime causes a brilliant tint to become paler with an evident “old”aspect and a significant loss of appeal.

At the same time the dye that is released in the washing liquor can beabsorbed by a white or a light coloured item, changing the originalcolour in an undesired way. The above issues are among the majorconcerns for the domestic laundry in the present market.

The textile industries are using a variety of different dyes and avariety of different processes to produce coloured items, depending ondifferent fibres and textiles.

Among dyes, the kind that gives most of the described issues is a dyecategory used for cotton and known as ‘direct’ dyes. These are also thedyes which are most used by textile industries.

In the recent years, some of the producers of chemicals for domestic usehave launched on the market some ‘absorbing’ sheets that are claimed ascapable to prevent the colour transfer and, more recently, also thecolour fading. What those sheets do is simply to absorb some of the dyesthat are released in solution by the coloured garments, becomingcoloured themselves, and giving the user the impression to have capturedall of the ‘dangerous’ dyes that could ‘stain’ their whites. One of theknown solutions of using a dye scavenger sheet comprising a cellulosicsubstrate material bearing a dye scavenger chemical is disclosed by U.S.Pat. No. 4,380,453.

If on one side it is true that those scavenger sheets are capable tocapture some of the dyes, it is also true that this kind of action isnot enough to prevent safely a colour transfer.

Even if in the professional market colour protectors are used in apre-treatment, i.e. before an industrial washing cycle, neverthelessthis kind of treatment has remained during years confined in theprofessional washing market. The main component of these known colourprotectors belong to a class of organic substances known as quaternaryammonium salts or “quats”. They have a general formula R₄N⁺X⁻ where Rrepresents an organic radical and X⁻ is a compatible anion:

R¹ is usually a C₁₂ to C₂₂ alkyl or alkenyl chain; R², R³ and R⁴ areindependently selected from C₁ to C₄ alkyl chains. A usual compound ofthis type is the quaternary ammonium compound cetyl trimethyl quaternaryammonium bromide.

But of course there is a number of different quats, with a number ofdifferent usages, including disinfection, fabric softening, colourprotection and so on.

It is an object of the present invention to provide a method for washingcoloured clothes in a domestic washing machine which can avoid or limitcolour fading and/or colour transfer, and without the need of using dyescavenger sheets or similar devices.

The above object is reached thanks to the features listed in theappended claims.

The applicant has discovered that with a modification of the normalwashing cycle and with the addition of a commercial additive containinga colour protector it is possible to have very good results in terms oflow colour fading and colour transfer, surprisingly comparable with theresults obtained in professional washing market where specific colourprotectors are used.

Surprisingly, the applicant has discovered that by using a rinseconditioner (known also as “fabric softener”) in a preliminary wettingphase before the usual washing program, the amount of quaternaryammonium compound contained in the commercial rinse conditioner issufficient for getting good result in terms of colour fading and colourtransfer, without any interaction problems with other compoundscontained in the rinse conditioner. This has the further advantage ofnot adding another chemicals to the ones already used during washingcycle.

According to another feature of the present invention, in order to limitthe negative interaction between the quaternary ammonium compound andthe anionic surfactants contained in the detergent used in the washingphase, after the preliminary wetting phase with water and additivecontaining the colour protector compound, the laundry undergoes aspinning phase for removing at least the major quantity of suchcompound.

Given the above similarity between the colour protectors compounds andthe fabric softener (particularly as far as the common active compoundis concerned), the applicant has designed for a domestic washer aspecific cycle for the coloured garments that includes a pre treatmentbefore the washing phase. This specifically designed pre-treatment mayuse both the fabric softener as well as a specific product for thecolour protection. The overall result is a washing cycle that cleans thecoloured garments but at the same time limits or avoids the twoundesired effects of colour fading and colour transfer. The availabilityof this cycle in a domestic washing machine gives to the user thepossibility to wash garments of different colours and also whitegarments without the need of sorting them.

Further advantages and features of a method and of a washing machineaccording to the invention will become clear thanks to the followingdetailed description, with reference to the attached drawings in which:

FIG. 1 is an experimental chart showing the result of tests on thebehaviour of white samples added to a 2 kg cotton load referring to theoriginal reflectance value and variations measured after the first,second, third and fourth washing cycle and by using or not using amethod according to the invention;

FIGS. 2-4 are experimental charts showing the results of a series oftests carried out using coloured samples (red, blue and blackrespectively) added to a 2 kg cotton load.

With reference to the drawings, the tests have been done using colouredtest specimens that, if washed in a normal cycle, release the dye. Thewashing machine used for the test is a commercial Whirlpool washer AWO/D6188 WP (8 kg) modified in order to carry out the preliminary phaseaccording to the invention. The detergent used for all tests is 60 ml of“Perlana Nero Assoluto” produced and sold by Henkel.

The specimen are used in the ISO testing for the colour transfer and arecoloured using dyes belonging to the group of the so called ‘directdyes’, which are the dyes more critical from the point of view of thecolour fading and transfer.

The measurement on these specimens has been done using the samecolorimeter used for the measurement of the soil removal.

The desired effect is that the white remains white (so keeping a highpercentage of reflectance) and the intense colour remain intense (sokeeping a reflectance value as low as possible).

The chart of FIG. 1 shows the behaviour of the white sample referring tothe original reflectance value and the variation measured after thefirst, second, third and fourth washing cycle.

The comparison is among the use of the detergent only (including apreliminary phase with water only), the pre-treatment done with 30 ml ofa commercial fabric softener Downy (Procter & Gamble—containing about15% of quaternary ammonium cationic compounds) and about 10 litres ofwater, and a pre-treatment done with 30 ml of a professional colourprotector produced and sold by the company Alberti Angelo in the sameamount of water used for the commercial fabric softener.

The Y axis shows the percentage of variation of the reflectance.

It is immediately evident from FIG. 1 that the fabric softener and thecolor protector are capable to preserve better the white (higherreflectance value) than the detergent only. Some variation in themeasurement are normally caused by the measurement noise but, despite ofthat, the trend is absolutely evident.

The measurement done on the red samples (FIG. 2) shows a clear increaseof the ‘whiteness’ of the sample, that means simply a fading of theoriginal color, when the pre-treatment is not used (detergent only).

It is absolutely evident that the pre-treatment with both chemicals(softener and professional protector) reduces substantially the fading,preserving the brilliance and the sharpness of the color for a longertime. It is also clear that if the garment looses less color, there isless dye in solution that can be transferred to other items.

The blue specimen (FIG. 3) behaves in a very similar manner. Once againthere is a clear evidence of color protection with both chemicals.

The black sample (FIG. 4) shows a quite surprising trend to increase thecolor intensity. This may be due to a starting value of reflectance thatis very low (the absolute magnitude is around 4% of reflected light) andso even small variations due to the noise of the measurement areamplified by the low reference figure. Despite of that, the trend of theprotection effect is well visible.

As shown in the charts, there is evidence of color protection andreduction of colour transfer by using both the fabric softener andprofessional protector. Very similar results have been obtained by usingother commercial fabric softeners, particularly “Fabuloso concentrato”(30 ml) produced and sold by Colgate, W-pro fabric softner produced andsold by the applicant (30 ml), Carrefour softner (25 and 50 ml). Thecontent of ammonium cationic compounds in “Fabuloso concentrato” (asdeclared by the producer) is higher than 25%, while in the other twosofteners it is above 15%.

In general, good results in terms of colour protection are obtained witha concentration of the commercial fabric softener comprised between 1and 10 ml of softener per litre of water, i.e. a volume concentrationbetween 0.1% and 1%.

Unfortunately, the behaviour of the two chemicals (softner and colourprotector) interferes with the action of the detergent. Cationicssurfactants (fabric softener) and in general the quats, react with theanionic surfactant of the detergents forming unsoluble compounds. Thiscauses two different, undesired effects:

-   -   the concentration of the available anionic surfactant decreases,        decreasing the cleaning power of the washing solution;    -   the insoluble compound may precipitate on garments or on washer        surfaces; this may cause spots on the garments and, in the long        run, deposition of sludge on the washer.

In order to minimize the interaction between the color protection andthe washing action, it is important to reduce as much as possible theamount of quats remaining in the solution after pre-treatment.

The above is achieved by increasing the spin speed between thepre-treatment and the main wash or even by introducing a rinse stepafter pre-treatment. The applicant has discovered that the concentrationof ammonium compounds on the fabric even after a water rinse step issufficient for yielding the colour protection effect.

Temperature, duration, chemical concentration, spin speed, are among theparameters that require tuning to get the optimal performance, dependingalso on the washing machine used and on the fabric softener used. Thistuning can be easily done by a person skilled in the art of designingwashing machines.

The pre-treatment has been preferably structured as follows:

-   -   pre-fill of clean water;    -   introduction of the protective chemical by water flow, while        tumbling;    -   heating to a predetermined temperature, preferably between 5° C.        and 30° C., while tumbling;    -   tumbling for a predetermined time (usually comprised between 5′        and 20′) to mix carefully;    -   drain of the used liquor;    -   spin extraction.

At the end of the above steps, the normal washing cycle will start,which can be preceded by the already mentioned extra rinse phase.

In conclusion, there is a clear evidence that the pre-treatmentaccording to the invention works for the color protection and brings aclear advantage for the consumer using a domestic washer. It protectsthe colors, particularly of cotton garments, maintaining for much longerthe original brightness.

The experiments done so far by the applicant show without any doubt thatthe theory works and the special cycle according to the inventiondelivers an unmatched result in a domestic washer as far as colourprotection is concerned.

The modifications of a usual washing machine in order to make it fit forcarrying out a method according to the invention are quite limited. Inthe detergent and additives distributor it is necessary to add acontainer or drawer which can be flushed by water into the tub and theuser interface has to be provided with a button or knob which is relatedto the special “colour” program, driven by a control process unit whichcontrols either the amount of water to be added in the preliminary step,the duration of tumbling, the temperature to be reached in suchpreliminary phase and the final spinning speed and time.

1-8. (canceled)
 9. A method of washing coloured clothes in a domesticwashing machine having a tub and a rotatable drum located within thetub, the method comprising: a washing phase where a detergent solutionis added to the tub and the drum is rotated within the detergentsolution; and a pre-washing phase, preceding the washing phase,comprising: water and an additive containing a colour protector compoundare added to the tub to form a pre-treatment solution; rotating the drumto tumble clothes in the drum in the pretreating solution to wet theclothes within the drum with the pretreating solution; and spinning thedrum to extract at least a portion of the pre-treatment solution fromclothes.
 10. The method according to claim 9, wherein the pre-treatmentsolution is between 5° C. and 30° C.
 11. The method according to claim10, wherein the pre-treatment solution is heated.
 12. The methodaccording to claim 9, wherein the pre-washing phase comprises, after thespinning the drum, rinsing the clothes in the drum with water.
 13. Themethod according to claim 9, wherein the rotating the drum to tumbleclothes occurs for a predetermined time.
 14. The method according toclaim 13, wherein the predetermined time comprises 5 to 20 seconds. 15.The method according to claim 9, wherein the pre-washing phase comprisesdraining the extracted portion of the pre-treatment solution.
 16. Themethod according to claim 15, wherein the draining occurs prior to thespinning the drum to extract.
 17. The method according to claim 9,wherein the colour protector compound is a quaternary ammonium compound.18. The method according to claim 17, wherein the additive is acommercial rinse conditioner.
 19. The method according to claim 17,wherein the concentration of rinse conditioner in water is between 1ml/l and 10 ml/l.
 20. The method according to claim 9, wherein, afterthe washing phase, a rinsing phase where fresh water is added to the tuband the drum is rotated.
 21. The method according to claim 20, wherein,after the washing phase and prior to the rinsing phase, an extractionphase where the drum is spun to remove the detergent solution from theclothes.
 22. A method of washing coloured clothes in a domestic washingmachine having a tub and a rotatable drum located within the tub, themethod comprising: a washing phase wherein a detergent solution isprovided onto clothes within the drum; a pre-washing phase, precedingthe washing phase, comprising providing a pre-treatment solutioncomprising water and an additive containing a colour protector compoundonto clothes in the drum, followed by an extracting of at least aportion of the pre-treatment solution from the clothes; and a rinsingphase, after the washing phase, where the detergent phase is rinsed fromthe clothes.
 23. The method of claim 22, wherein the pre-washing phasecomprises tumbling the clothes in the pretreating solution to wet theclothes.
 24. The method of claim 22, wherein the pre-washing phasecomprises draining the extracted portion of the pre-treatment solution.25. The method of claim 22, wherein the pre-washing phase comprises,after the extracting, rinsing the clothes in the drum with water. 26.The method of claim 22, wherein the colour protector compound is aquaternary ammonium compound.
 27. The method of claim 22, wherein theadditive is a commercial rinse conditioner.
 28. The method of claim 27,wherein the concentration of rinse conditioner in water is between 1ml/l and 10 ml/l.